Mullitization behaviour of alumina enriched clay inpresence of dopant fe2o3

Abstract

Mullatization behaviour of china clay with reactive alumina sources has been studied. The calcined clay was ground then mixed with reactive alumina. These raw material are mixed with different amount of iron oxide (vig. 0% Fe2O3,, 1.5% Fe2O3, 3% Fe2O3, 4.5% Fe2O3,, 6% Fe2O3). Rectangular bars and pallets were sintered at different temperatures (vig. 14500C, 15500C, 16500C) with a soaking period of 2 hrs. A holding in temperature was done to accommodate binder burn out. Previously the characterizations of the raw materials were carried by XRD analysis, DSC, TG. The X-ray and microstructural analysis were to understand the mullatization behaviour of the china clay. The calcined clay derived samples were used as they show better physical and mechanical properties and it shows very low shrinkage. The fired samples fired at 16500C shows more than 98% mullite formation in the body but they differ in their grain size. With increase in the percentage iron oxide there is not significant change in the formation in the mullite formation at 16500C but the grain size increases continuously. The formation of needle like mullite grain increases with increases in the iron oxide content. With increase in the iron oxide content there is decrease in the amount in the unreacted free alumina. Microstructural studies on the sintered and polished samples and X-ray diffraction studies on the sintered specimens are carried out to estimate the mullitization of the individual samples fired at different temperatures. The formation of secondary mullite formation has been observed through inter-diffusion. The formation of primary mullite formation has been observed at lower iron oxide content through XRD analysis.